primefaces selectOneMenu未排序

Question

我的页面中有一个selectonemenu，我从我的支持bean获取其内容。但是selectonemenu的内容没有排序。这是代码......

    <p:selectOneMenu id="Department" value="#{search.selectedDepartment}">  
            <f:selectItem itemLabel="Select Department" itemValue="" />  
            <f:selectItems value="#{search.departments}" />  

        </p:selectOneMenu> 

和我的豆......

public class SearchBean implements Serializable {

private Map<String, Map<String, String>> courseData = new HashMap<String, Map<String, String>>();

private Map<String, String> departments = new HashMap<String, String>();
private String selectedDepartment;


    departments.put("department1",
            "department1");
    departments.put("department2",
            "department2");
    departments.put("department3", "department3");
departments.put("department4", "department4");
departments.put("department5", "department5");





//getters setters...


}

和selectonemenu的内容分别不是department1，department2，department3，department4，department5。它没有排序。

Answer 1

它没有排序，因为HashMap没有可预测的迭代顺序。请改为LinkedHashMap。

Answer 2

LinkedHashMap 它的排序没有排序，即按顺序排列，但如果使用 TreeMap ，则按字母顺序排序